Hydraulic jacks for low head room operation

ABSTRACT

An hydraulic jack having an elongated base and an elongated lifting head, there being crossing hydraulic rams connected between the base and head, and there being sets of leveling links connected between the base and head on opposite sides of the rams for jack-knifing movement in opposite directions when the jack is being operated, the hydraulic circuit to the rams including means for causing the two ram pistons to travel at the same speed.

United States Patent Inventor Donald ,Iuds

Waukcslu, Wis.

Appl. No 8] 7,474

Filed Apr. 18, I969 Patented Aug. 10, 1971 Assignee Milwaukee Hydraulic Products Corporation Milwaukee, Wis.

HYDRAULIC JACKS FOR LOW HEAD ROOM OPERATION 13 Claims, 7 Drawing Figs.

05. Cl 254/2 B, 254/122, 60/52 HE lut.Cl 860p 1/00, B66f 3/22 Field of Search 254/2 BC, 8, 9, 10, 122,93, 89 H; l87/l8; 92/61; 60/52 HE, 54.5

[56] References Cited UNITED STATES PATENTS 2,829,863 ,4/l958 Gibson 254/8 2,891,765 6/ l 959 Pearne 254/2 Primary Examiner-Robert C. Riordon Assistant Examiner-David R. Melton Attorney-Morse" and Morsell ABSTRACT: An hydraulic jack having an elongated base and an elongated lifting head, there being crossing hydraulic rams connected between the base and head, and there being sets of leveling links connected between the base and head on opposite sides of the rams for jack-knifing movement in opposite directions when the jack is being operated, the hydraulic circuit to the rams including means for causing the two ram pistons to travel at the same speed.

HYDRAULIC JACKS FOR LOW HEAD ROOM OPERATION BACKGROUND OF THE INVENTION I. Field of the Invention The present invention pertains to hydraulic jacks which are particularly useful in garages and service stations.

2. Description of the Prior Art I-Ieretofore the majority of hydraulic jacks for bumper engagement have been of the post type. With present car and bumper designs the head room below the portion of a bumper which should be engaged has become so small as to obsolete most of the post-type jacks for bumper engagement. This is due to the depending skirts which are now commonly used below the bumpers and which make it difficult to engage the strong part of a bumper with the conventional bumper jack. On one type of car the bumper has to be provided with special openings and the jack with special hooks for engaging in the openings. There have heretofore been lever-type jacks, which can be effectively collapsed for use where head room is low, but these jacks are principally adapted for use under the car to engage at one point only with a special portion of the car, and are not adapted for universal use. Furthermore, these levertype jacks are pushed in endwise and lack stability for many uses. Some of these prior lever jacks are disclosed in Weaver Pat. No. 2,533,980, and in Johnson Pat. No. 2,806,613.

SUMMARY OF THE INVENTION The present invention provides a low head room jack having a relatively long base and a relatively long lifting head, both extending transversely of the direction which the jack is normally pushed during positioning, there being crossing hydraulic rams connected between the base and head which are obliquely disposed when the jack is in elevated condition, and there being sets of leveling and stabilizing links connected between the base and head, one set being on one side of the rams and the other set on the other side thereof. EAch set of links may include a pair of jackknifing parallelograms. The hydraulic circuit for the rams includes means which causes the two ram pistons to travel at the same speed during operation.

One of the objects of the present invention is to provide a jack which is strong and stable enough for any type of use but which, when in collapsed position, is so low that it may be readily engaged with bumpers of any of the modern vehicles or pushed underneath the side of any car if it is desired to engage a longitudinal frame member on one side or the other, or pushed under either the front or rear bumper to engage a front of rear subframe portion.

A further object of the invention is to provide a jack of the class described in which the lifting head extends transversely of the normal direction of movement of the jack when it is being pushed under a car, and in which the lifting head is relatively long to provide for engagement throughout a substantial portion of the length of a frame part in order to provide greater stability during the lift.

A further object of the invention is to provide an improved jack with a long lifting head having novel means for causing both ends of the head to travel at the same speed and thereby maintain a level and centered condition.

A further object is to provide a jack which is constructed to readily receive spaced bumper adapters and to cause both adapters to travel at the same speed during jack operation.

' A further object of the invention is to provide a jack which is stable and rigid and which is constructed to resist twisting forces.

A further object of the invention is to provide an improved jack of the class described which is relatively simple in construction and operation, strong and durable, and well adapted for the purposes described.

With the above and other objects in view, the invention consists of the improved hydraulic jack for low head room operation, and all of its parts and combinations as set forth in the claims, and all equivalents thereof.

BRIEF DESCRIPTION OFTHE DRAWINGS In the accompanying drawing, in which the same reference numerals designate the same parts in all of the views:

FIG. I is a partially diagrammatic vertical sectional view showing the crossing rams in an elevated position and showing an hydraulic circuit;

FIG. 2 is a view looking at the front of an automobile, showing the jack in engagement with the front bumper, the jack being shown partially in perspective and the lifting head having a bumper adapter thereon;

FIG. 3 is a perspective view showing the jack in an elevated condition, part of the handle being broken away;

FIG. 4 is a fragmentary perspective view looking principally at the top of the base and showing the connections between the lower ends of the ram cylinders and the base as well as the connections between the lower ends of the leveling links and the base;

FIG. 5 is a perspective view showing the jack in completely collapsed condition, the handle being broken off;

FIG. 6 is a fragmentary detail view looking at one of the ends of the lifting head and showing a portion of a bumper adapter thereon, part being broken away and shown in section; and I FIG. 7 is a sectional view taken on the line 7-7 of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to the drawing, the numeral 20 designates a base having end tubes 21, each carrying wheels 22. Connecting the end tubes on each side are spaced metal bars 23 and 24, as shown in FIG. 4. Between the bars 24 is an additional bar 25. Pivoted between one of the bars 24 and the bar 25 near one end of the base is the lower end of a primary cylinder 26, the cylinder having a piston 27 operable therein (see FIG. I), and there being a tubular piston rod 28 projecting from the cylinder, the cylinder and piston constituting a first hydraulic ram. Pivotally mounted between the other one of the bars 24 and bar 25 near the opposite end. of the base, as shown in FIG. 4, is the lower end of a second or follower cylinder 29. The second cylinder has a piston 30 operable therein and carrying a tubular piston rod 31. The upper end of the piston rod 28 is pivotally connected as at 32 within the lower portion of an I-beam near one end thereof, said I-beam forming an elongated lifting head 33. The upper end of the other piston rod 31 is pivotally connected as at 34 with the lifting head 33 near the opposite end. The outer sides of the two cylinders are equipped with coacting rub strips 35 (see FIGS.

3 and 4) which bear against each other during operation. The rub strip 35 for the cylinder 29 can be seen in FIG. 3, and the rub strip for the cylinder 26 in FIG. 4.

Pivotally connected as at 36 (FIG. 4) between the bar 23 and the bar 24 on one side are the lower ends of parallel links 37. The latter have forked upper ends between which the lower ends of upper parallel links 38 are pivoted, as at 39, there also being transverse links 40 which have their ends pivotally connected at the pivots 39. Thus the lower set of links forms a parallelogram linkage.

On the opposite side of the base near the opposite end thereof the lower ends of parallel links 41 are pivotally connected between the bars 23 and 24 on said other side. The links 41 are constructed and connected the same as the links 37, and pivotally connected to their upper ends as at 42'are the lower ends of upper links 43 which correspond to the links 38 on the first side. There are also transverse links 44 which correspond with the transverse links 40 and which are similarly pivoted. The upper ends of the parallel links 38 are pivotally connected as at 45 to one of the sides of the lifting head 33 near one end thereof, as shown in FIG. 3. The upper ends of the links 43 on the other side are pivotally connected as at 46 to the other side of the lifting head near the opposite end thereof, as shown in FIG. 3. While the sets of parallelogram linkage on the two sides of the device are illustrated as jackknifing in opposite directions, this is not essential as the sets of linkage can be arranged to jackknife in the same direction.

The lifting head is adapted to removably receive and support an elongated adapter 47, part of which is shown in FIGS. 6 and 7. The adapter is a hollow, boxlike structure and has an extension tube 48 slidable therein on one side in the slideway 49. A similar slide 50 is slidable out of the opposite end of the adapter in the slideway 51. The outer end of each of the slides 48 and 50 is tubular in a vertical direction to slidably receive posts 52, each post having a top bumper-engaging pad 53. Each post also has vertically spaced apertures 54 so that the post may be held in an adjusted position by a pin 55 (see FIG. 2). At each end of the adapter 47 is a depending tongue 56 which is received in an eye 57 at the end of the lifting head to detachably hold the adapter in position when it is being used.

Suitably mounted on the base in any desired location is a pump 58 and a reservoir 59. The pump is operated by a handle 60 which may be manipulated to create pumping strokes. One suitable pump is fully disclosed in my Pat. No. 3,329,403. Any suitable type of pump may be employed, including a motor driven pump. Fluid under pressure from the reservoir 59 is delivered by the pump 58 through lines 61 and 62, past control valve 73, into the lower end of the primary cylinder 26. While various ways of causing the piston rods 31 and 28 to travel at the same speed may be employed, FIG. 1 discloses a novel and fool-proof arrangement. In the cylinder 26 the piston 27 is surrounded by seals 63 which prevent the body of fluid 64 below the piston from moving past the piston. In the remainder of the hydraulic system is a confined body of hydraulic fluid 65. Part of this fluid is in the upper portion of the cylinder 26 above the piston 27. It is in communication through port 66 at the lower end of the piston rod 28 with the inner chamber 67 of said tubular piston rod. Fluid in this chamber is in communication through a line 68 with the chamber 69 of the other piston rod 31. The lower end of the chamber 69 opens through the bottom of the piston 30 as at 70 into communication with the portion of the cylinder 29 which is below the piston 30. There is also restricted communication around the piston 30 as there are no sealing rings around the latter. In addition, the chamber above the piston 30 in the cylinder 29 is in communication through port 72 with the interior chamber 69 of the tubular piston rod 3 l. This closed hydraulic system is always filled to capacity with hydraulic fluid, as is clear from FIG. 1. The two cylinders, pistons and piston rods are all of the same size, and the crosssectional area (a) at the CD. of the piston rods 28 and 31 is equal to the cross-sectional area of the annular space, in either cylinder, which surrounds the tubular piston rod 28 or 31.

OPERATION In operation, when the jack is in the lowered position of FIG. it requires so little head room that it may be readily pushed under either side of a car to engage a longitudinal frame member on one side to lift up both wheels on this side. Due to the length of the lifting head 33 there is stability during such lifting. It is also possible to push the jack under either the front or rear bumper to engage a front or rear subframe portion. Also, if it is desired to lift a car by the bumper, as in FIG. 2, then the adapter may be put in place and the lifting posts 52 adjusted to meet conditions.

When the pump handle 60 is manipulated, by being reciprocated up and down, it will force hydraulic fluid from the reservoir into the lower portion of the primary cylinder 26. When the jack is in the collapsed condition of FIG. 5. the piston 27 is substantially at the bottom of the cylinder 26, as is the piston 30 in the cylinder 29. As the pump is operated, lifting pressure will be exerted on the piston 27 to move it upwardly in the cylinder 26. As the piston 27 moves upwardly the piston rod 28 moves upwardly, and fluid in the portion of the closed system comprising the chamber 65 will be forced through the port 66 into the tubular chamber 67 of the piston 28. Fluid will also be forced through the line 68 and tubular chamber 69 of the other piston rod into the lower end of the cylinder 29 through the port 70. This will cause the piston 30 to be moved upwardly in its cylinder 29 at the same rate of speed as the piston 27. The cross-sectional area (a) through the piston rod 31 is such (being equal to the cross-sectional area of the annular space surrounding the rod) that as the piston 30 moves upwardly there is sufficient additional space created in the cylinder 29 (below the piston 30) to accommodate the fluid which is displaced during the upward movement of the piston 27 in the cylinder 26. The cross-sectional area of the annular space around the piston rod 28 of the cylinder 26 is also equal to the cross-sectional area of the CD. of the piston rod 28. This relationship and the other dimensions (the two pistons and cylinders being of the same size) are so worked out that the pistons travel at the same rate of speed so that the lifting element moves straight upwardly with the same amount of lift on each end.

When the operation of the pump has been stopped a valve 73 may be operated, either manually or automatically, to hold the parts in a selected position. When it is desired to lower the jack, the valve 73 may be manipulated to open the line 62. This will permit a gravity return of the fluid from the chamber 64, through the pump 58, back into the reservoir. During such movement fluid in the lower portion of cylinder 29 can move back through the opening into the interior of the piston rod 31, causing a back movement of fluid through the chamber 67 of piston 28 and line 68 back into the chamber 65 of cylinder 26 to keep the space above the piston filled as the piston 27 is lowered by gravity. Due to the dimensional relationships heretofore referred to, the lowering movement of the two pistons will be at the same speed so that the lowering movement will be equal at both ends of the lifting head.

During operation, the two cylinders brace against each other as the rub strips 35 slide one against the other.

Each of the sets of links connecting the base with the head on either side of the rams comprises a pair of parallelograms which jackknife during operation. It is to be noted that the linkage on one side jackknifes in one direction, as shown in FIGS. 3 and 4, and the linkage on the other side jackknifes in the opposite direction. These links insure that the lifting head is kept level. If there were no links the lifting head might be overbalanced on one side or the other. The rubbing contact between the cylinders, together with the linkage, creates rigidity against twisting forces during use,

What I claim is:

1. A jack comprising a base, an elongated lifting head, an hydraulic ram assembly connected at one end to said base and at its other end to the lifting head and having a piston, a second hydraulic ram assembly connected at one end to said base and at its other end to said head and having a piston, and means including hydraulic circuits for said rams for causing the rams to move at the same rate of speed during operation of the jack, which means includes a closed hydraulic chamber below the piston in a first cylinder for one of the ram assemblies, means for introducing hydraulic fluid under pressure into said chamber to cause movement of said piston, a tubular piston rod projecting from said piston and having its interior in communication with the space above the piston, a second cylinder having a piston and a like tubular piston rod of the same size for the other ram assembly, there being a second closed hydraulic circuit which includes those portions of the second cylinder both above and below the piston, which portions are in communication with each other, which includes the interior of the tubular piston rod for said second cylinder, and which includes the interior of the tubular piston rod of the first cylinder as well as the chamber above the piston of the first cylinder, which second closed circuit is maintained filled with hydraulic fluid at all times, and there being means affording communication between the upper ends of the two tubular piston rods and between the interior of the piston rod for the second cylinder and said cylinder, the size relationship between the working parts of the two ram assemblies being such as to cause the rams to move at the same rate of speed during operation of the jack.

2. A jack as claimed in claim 1 in which the cross-sectional area through the CD. of each piston rod is the same and is equal to the cross-sectional area of the annular space within each cylinder which surrounds the piston rod.

3. A jack comprising a base having opposite ends, an elon-' gated lifting head having opposite. ends, an hydraulic ram assembly pivotally connected at one end to said base toward one end thereof, and at its other end to the lifting head toward the opposite end of the latter, and an hydraulic ram assembly in crossing relationship with said first ram assembly pivotally connected to said base toward the opposite end from the connection for the first ram assembly and'pivotally connected to the lifting head in a location toward the opposite end from the connection for the first ram assembly.

4. A jack as claimed in claim 3 in which there is collapsible leveling linkage pivotally connected between the lifting head and base.

5. A jack as set forth in claim 3 in which each rarn assembly includes a cylinder and in which adjacent sides of the cylinders have rub strips thereon which are in crossing relationship with one another and which are in rubbing contact during operation of the jack.

6. A jack as claimed in claim 3 in which there is a set of collapsible leveling links on one side of the rams arranged for jackknifing movement in one direction during lowering of the jack and in which there is a set of collapsible leveling links on the other side of the rams arranged for jackknifing movement in the opposite direction during lowering of the jack, said leveling links being connected between the base and lifting head.

7. A jack as claimed in claim 4 in which the collapsible leveling linkage includes upper and lower parallelogram linkage on each side of the ram assembly positioned for collapsible jackknifing movement in opposite directions from one another.

8. A jack as claimed in claim 3 in which there is means for causing the rams to move at' the same rate of speed during operation of the jack.

9. A jack as claimed in claim 3 in which there is means including hydraulic circuits for said rams for causing the rams to 1 move at the same rate of speed during operation of the jack.

It). A jack as claimed in claim 7 in which the means for causing the rams to move at the same rate of speed comprises: a closed hydraulic chamber below the piston in a first cylinder for one of the ram assemblies, means for introducing hydraulic fluid under pressure into said chamber to cause movement of said piston, a tubular piston rod projecting from said piston and having its interior in communication with the space above the piston, a second cylinder having a piston and a like tubular piston rod of the same size for the other ram assembly, there being a second closed hydraulic circuit which includes those portions of the second cylinder both above and below the piston, which portions are in communication with each other, which includes the interior of the tubular piston rod for said second cylinder, and which includes the interior of the tubular piston rod of the first cylinder as well as the chamber above the piston of the first cylinder, which second closed circuit is maintained filled with hydraulic fluid at all times, and there being means affording communication between the upper ends of the two tubular piston rods and between the interior of the piston rod for the second cylinder and said cylinder, the size relationship between the working parts of the two ram assemblies being'such as to cause the rams to move at the same rate of speed during operation of the jack.

11. A jack as claimed in claim [0 in which the cross-sectional area through the 0.D. of each piston rod is the same and is equal to the cross-sectional area of the annular space within each cylinder which surrounds the piston rod.

12. A jack as claimed in claim 3 in which the base and lifting head are both elongated and parallel and in which there is a handle connected to the base intermediate its length.

13. A jack as set forth in claim 3 in which there is means including a first hydraulic circuit for the first ram for causing movement of said first ram, and in which there is means includin a second hydraulic circuit which is common to both hydrau ic rams for causing the second hydraulic ram to follow movement of the first hydraulic ram and at the same rate of speed. 

1. A jack comprising a base, aN elongated lifting head, an hydraulic ram assembly connected at one end to said base and at its other end to the lifting head and having a piston, a second hydraulic ram assembly connected at one end to said base and at its other end to said head and having a piston, and means including hydraulic circuits for said rams for causing the rams to move at the same rate of speed during operation of the jack, which means includes a closed hydraulic chamber below the piston in a first cylinder for one of the ram assemblies, means for introducing hydraulic fluid under pressure into said chamber to cause movement of said piston, a tubular piston rod projecting from said piston and having its interior in communication with the space above the piston, a second cylinder having a piston and a like tubular piston rod of the same size for the other ram assembly, there being a second closed hydraulic circuit which includes those portions of the second cylinder both above and below the piston, which portions are in communication with each other, which includes the interior of the tubular piston rod for said second cylinder, and which includes the interior of the tubular piston rod of the first cylinder as well as the chamber above the piston of the first cylinder, which second closed circuit is maintained filled with hydraulic fluid at all times, and there being means affording communication between the upper ends of the two tubular piston rods and between the interior of the piston rod for the second cylinder and said cylinder, the size relationship between the working parts of the two ram assemblies being such as to cause the rams to move at the same rate of speed during operation of the jack.
 2. A jack as claimed in claim 1 in which the cross-sectional area through the O.D. of each piston rod is the same and is equal to the cross-sectional area of the annular space within each cylinder which surrounds the piston rod.
 3. A jack comprising a base having opposite ends, an elongated lifting head having opposite ends, an hydraulic ram assembly pivotally connected at one end to said base toward one end thereof, and at its other end to the lifting head toward the opposite end of the latter, and an hydraulic ram assembly in crossing relationship with said first ram assembly pivotally connected to said base toward the opposite end from the connection for the first ram assembly and pivotally connected to the lifting head in a location toward the opposite end from the connection for the first ram assembly.
 4. A jack as claimed in claim 3 in which there is collapsible leveling linkage pivotally connected between the lifting head and base.
 5. A jack as set forth in claim 3 in which each ram assembly includes a cylinder and in which adjacent sides of the cylinders have rub strips thereon which are in crossing relationship with one another and which are in rubbing contact during operation of the jack.
 6. A jack as claimed in claim 3 in which there is a set of collapsible leveling links on one side of the rams arranged for jackknifing movement in one direction during lowering of the jack and in which there is a set of collapsible leveling links on the other side of the rams arranged for jackknifing movement in the opposite direction during lowering of the jack, said leveling links being connected between the base and lifting head.
 7. A jack as claimed in claim 4 in which the collapsible leveling linkage includes upper and lower parallelogram linkage on each side of the ram assembly positioned for collapsible jackknifing movement in opposite directions from one another.
 8. A jack as claimed in claim 3 in which there is means for causing the rams to move at the same rate of speed during operation of the jack.
 9. A jack as claimed in claim 3 in which there is means including hydraulic circuits for said rams for causing the rams to move at the same rate of speed during operation of the jack.
 10. A jack as claimed in claim 7 in which the means for causing the rams to move at the sAme rate of speed comprises: a closed hydraulic chamber below the piston in a first cylinder for one of the ram assemblies, means for introducing hydraulic fluid under pressure into said chamber to cause movement of said piston, a tubular piston rod projecting from said piston and having its interior in communication with the space above the piston, a second cylinder having a piston and a like tubular piston rod of the same size for the other ram assembly, there being a second closed hydraulic circuit which includes those portions of the second cylinder both above and below the piston, which portions are in communication with each other, which includes the interior of the tubular piston rod for said second cylinder, and which includes the interior of the tubular piston rod of the first cylinder as well as the chamber above the piston of the first cylinder, which second closed circuit is maintained filled with hydraulic fluid at all times, and there being means affording communication between the upper ends of the two tubular piston rods and between the interior of the piston rod for the second cylinder and said cylinder, the size relationship between the working parts of the two ram assemblies being such as to cause the rams to move at the same rate of speed during operation of the jack.
 11. A jack as claimed in claim 10 in which the cross-sectional area through the O.D. of each piston rod is the same and is equal to the cross-sectional area of the annular space within each cylinder which surrounds the piston rod.
 12. A jack as claimed in claim 3 in which the base and lifting head are both elongated and parallel and in which there is a handle connected to the base intermediate its length.
 13. A jack as set forth in claim 3 in which there is means including a first hydraulic circuit for the first ram for causing movement of said first ram, and in which there is means including a second hydraulic circuit which is common to both hydraulic rams for causing the second hydraulic ram to follow movement of the first hydraulic ram and at the same rate of speed. 